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Marine space is about to get even busier. Around the globe many countries are looking to use their ocean space, especially their coastal marine areas, for the extraction of renewable energy from the wind, waves and tides. This large scale use of renewable energy will help global reductions in CO2 release and ultimately reduce the risk of ecological damage due to sever climate change. However the cumulative...
In this paper, performance of an underwater acoustic OFDM system is studied for various pilot allocation schemes having different pilot spacings in the frequency and time domain. The underwater OFDM system is first developed to support different pilot allocation schemes, and the experiments is conducted at the western sea near Janggohang, South Korea in July 2016. The system performance is, then,...
A method of estimating the source depth of wideband underwater acoustic pulses in deep water is proposed in this paper. The method is based on the characteristic of frequency domain interference oscillation of broadband signals received at a single stationary hydrophone. The oscillation period is related to the Lloyd's Mirror effect (LME) and can be transformed into the information of source depth...
In this paper, we investigate the performance of HFM signals for timing synchronization in underwater acoustic communication systems. The considered HFM signals are comprised of up-sweep and down-sweep HFM signals having different bandwidth. The synchronization performance of the proposed HFM is then evaluated numerically using the channel model constructed based on western sea of South Korea. Numerical...
In order to detect quiet submarines, an important trend in underwater acoustics is the use of large arrays with many elements in an effort to detect weak signals. In recent years, vector sensors have been widely used in sonar equipment. Compared with sound pressure array, vector array can be used to expand array aperture to improve processing gain, and overcome the problem of left and right ambiguity...
Self-calibration methods of underwater light attenuation using a multispectral imaging system are important for subsea detection. However, the accuracy of calibration is strongly related to the characteristics of color filters used in imaging systems. This paper presents the influence of filters on attenuation calibration. The principle of a self-calibration method is introduced with the origin of...
This paper describes the specific challenges to measure the ocean currents in the narrow channel of the Raz Blanchard by means of an ocean radar pair. The ocean current velocities in this area are extreme high, up to 5 m/s and are changing fast. In addition to this, the ocean wave parameters should be measured as well. These boundary conditions are challenging for any oceanographic measurement equipment...
In most of the current operational autonomous underwater vehicles (AUVs), a survey mission is generally composed of two main stages. The first one conducts an exhaustive coverage over an area of interest, while gathering data of the sea bottom. Then, and after processing the collected data, a second mission is programmed to obtain more detailed information of potential targets, and to cover the gaps...
The article is about the development of a sealing system for pressure housings made of ultra-high performance concrete (UHPC), which has been developed within the Helmholtz Alliance “ROBEX” (robotic exploration of extreme environments) [1]. Several kinds of sealing systems according to the material properties of concrete have been designed so far and the amount of aluminum or titanium needed has been...
Heavy metal ion pollution emerges as a potential threat to humankind and the ecosystem due to their increased spreading into the environment. Detection of highly toxic heavy metal ions requires rapid, simple, sensitive and selective detection methods in water environments. Optical fibre sensors facilitate the remote, continuous and in-situ detection due to their inherent properties. Herein, we report...
In this study, SAR oil spill observation is investigated for different polarizations, incidence angles and wind conditions. The dataset is composed by a time-series of 42 TerraSAR-X dualpol SAR images acquired between July 2011 and April 2016. The incidence angle, wind speed and polarization dependency for oil spill observation is shown for the first time using a large time-series of the same oil...
In this study, TanDEM-X full-polarimetrlc bistatic and monostatic imagery are exploited for maritime applications purposes. The Mueller matrix and the phase difference between co-polarized channels (CPD) are exploited to deal with both the monostatic and the bistatic scenes. Subtle differences are found between the Mueller matrix collected in bistatic/monostatic mode; while similar performance is...
When a submerged target is crossing the source-receiver line, the aberration in the received acoustic field and Doppler shift in the forward scattered field are simultaneously induced. Formulations for the two variations are developed upon an ideal forward scattering configuration. Both the field aberration and Doppler shift are expressed as functions with the same argument — target motion time. The...
The optical satellite imagery with high resolution and large coverage has been widely applied to gain the geospatial information of island and reef area. In this paper, according to the repeated observation of satellites, the method of georeferencing with multi-source optical satellite imagery is presented, in which the constraint model is introduced in to solve the rank defect of the coefficient...
With the proliferation of exciting tools such as GPS, voice assistants, and cloud computing, advanced technology is in the hands of the average person more than ever before. In the field of marine technology, this is especially true. Previously only the most well-funded research programs could afford equipment such as Remote Operated Vehicles (ROVs), but in recent years more cost efficient solutions...
In this study, we investigated the effect of water temperature inversion layer on the propagation of acoustic wave in the western coastal sea of Jeju island in April 2015. When the acoustic source and receiver are simultaneously located within the water temperature inversion layer depth, the long range propagation of acoustic wave is confirmed by numerical modeling. This is caused by the duct effect...
The self-repairing composite materials integrated with sensing is way forward to reduce maintenance cost and increase consumer safety. In this work, the novel self-healing carbon fibre reinforced unidirectional bulk tape of simple architecture is prepared using nanocomposite film. The bulk material tape was prepared using nanocomposite film of low melting temperature polymer sandwiched between two...
Classification of submerged objects can be performed using broadband sonar and underwater sound scattering analysis. The backscattered signals, composed of specular echo and elastic echo, have information on the submerged target, including its dimensions and material characteristics. In this study, we performed shockwave-scattering simulations of backscattered signals when a broadband shockwave (1–60...
We applied blue LEDs to the prevention of the settlement of cyprids. The relatively strong intensity of the irradiation of ca. 500 (W m−2) could prevent the settlement of cyprids on the area of the bottom of a tub, above which the light source was adjusted. On the other hand, cyprids settled on the area on which the relatively weak intensity of the irradiation, < 100 (W m−2), was reached. In the...
An autonomous sensor platform powered by a benthic microbial fuel cell (BMFC) has been developed and deployed to supply hourly dissolved oxygen (O2), temperature and conductivity measurements from a remote location in the core of the oxygen minimum zone of the northeast Pacific. The platform uses a compact acoustic modem to both store and transmit sensor and energy harvesting measurements. Initial...
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